24.02.2020 20:23, Dmitry Osipenko пишет:

24.02.2020 19:33, Karel Zak пишет:

quoted

On Wed, Feb 19, 2020 at 09:59:54AM -0700, Stephen Warren wrote:

quoted

On 2/19/20 9:27 AM, Christoph Hellwig wrote:

quoted

On Wed, Feb 19, 2020 at 07:23:39PM +0300, Dmitry Osipenko wrote:

quoted

The gpt_sector=<sector> causes the GPT partition search to look at the
specified sector for a valid GPT header if the GPT is not found at the
beginning or the end of block device.

In particular this is needed for NVIDIA Tegra consumer-grade Android
devices in order to make them usable with the upstream kernel because
these devices use a proprietary / closed-source partition table format
for the EMMC and it's impossible to change the partition's format. Luckily
there is a GPT table in addition to the proprietary table, which is placed
in uncommon location of the EMMC storage and bootloader passes the
location to kernel using "gpt gpt_sector=<sector>" cmdline parameters.

This patch is based on the original work done by Colin Cross for the
downstream Android kernel.

I don't think a magic command line is the way to go.  The best would be
to reverse-engineer the proprietary partition table format.  If that is
too hard we can at least key off the odd GPT location based of it's
magic number.

 +1

quoted

I thought that the backup GPT was always present in the standard location;

If they have proprietary stuff on begin of the device and valid backup
GPT at the end of the device then designer of this junk is crazy, because
many GPT fdisk-like tools will try to recover from the backup header and 
overwrite the unknown (invalid) stuff at the begin of the device...

It's a problem created by vendor, but these devices are assumed to run
Android-only. So it's not really that bad :)

Is there any way to mark parts of block device as read-only? Such that
userspace couldn't write to the RO-marked sectors, I guess that could
help to save someone's bacon.